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Old 09-22-2015, 12:55 PM   #1
88_Blue_Brick
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So my 1988 244 DL has been running pretty rich. It misfires at idle, and you can see a bit of black smoke. I checked the 02 sensor with a multimeter and it was steady at 0.860v at idle. I raised the RPM until it ran smooth (no longer misfiring) and the reading stayed steady around 0.840v-0.860v. I then snapped the throttle and let the engine settle back down to idle. As the RPMs were coming back down, the sensor voltage dropped to lean, around 0.024v, before the engine settled back to idle. The voltage then climbed right up to 0.940v steady. I haven't had much time to look into anything in depth, but I don't think the car as any vacuum leaks, 19inHg at idle, the needle flutters but I believe this is due to it misfiring. If I bring the car off idle, it stops misfiring and the needle goes up to 21inHg and stops fluttering. The fuel pressure regulator is not leaking, and I replaced the engine coolant temperature sensor (not the one for the gauge) since it was cheap. I also checked the accordion tube and found no holes. What I want to do is check all the sensor voltage/resistance values at the computer connector to rule out wiring before I start throwing parts at it. Would a Haynes manual be of any use? I could pick one up today from the local Pep Boys. I've seen a lot of people mention Bentley manuals, but I'd have to order one and they cost way more than the Haynes manual. I've also skimmed through the Green Books, but didn't find the info I was looking for (I like numbers and parameters). Do I need to look more thoroughly? I also read that there is no real way to "test" the AMM outside of an electronics lab. Anyone else know otherwise? I don't really have the budget to buy a re manufactured Bosch AMM, and I don't know if I'd trust another brand.

Any help would be greatly appreciated. I normally deal with OBDII cars at work, so I'm used to seeing PIDs and having access to specs and parameters. This is my first foray into the pre-self-diagnostics, and it's proving to be an interesting adventure so far lol.
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Old 09-22-2015, 01:01 PM   #2
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Do not waste your money on anything other than a Bently "Bible". The info in the Bently manual is thorough and accurate. Chiltons and Haynes are good bird cage liner if you need some. Which ECT sensor did you put in? The 02 sensor is telling you the engine is running too rich.
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Old 09-22-2015, 01:15 PM   #3
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Between the crappy fuel economy, raw fuel smell, and O2 sensor reading, I'm well aware that it's running rich, believe me. The car smells like a go kart track. And I replaced the two prong temp sensor under the number 3 intake runner. I was hoping the sensor was reading full cold (open?) and that was making it run rich, but no such luck.
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Old 09-22-2015, 01:19 PM   #4
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I guess the question I should be asking is what would cause the computer to ignore the O2 sensor? I wanted to try to find specs on the various fuel system sensors so I could determine if the computer was actually "seeing" what the sensors were "seeing".
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Old 09-22-2015, 01:25 PM   #5
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What makes you think the ECU is ignoring the O2 sensor? I asked a specific question, which ECT sensor did you put in? Part number, where did you get it, Bosch or aftermarket?
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Old 09-22-2015, 01:34 PM   #6
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Originally Posted by 88_Blue_Brick View Post
I guess the question I should be asking is what would cause the computer to ignore the O2 sensor? I wanted to try to find specs on the various fuel system sensors so I could determine if the computer was actually "seeing" what the sensors were "seeing".
The ECT can be backprobed at the ECU connector. Just measure the voltage on the blue wire (pin 2) which supplies the thermistor from a 5V current limited source resulting in less than a volt when the motor is warm and as much as 3-4V when you are cranking the car on a below-zero arctic morning. If you see 5V there, you know the wiring is corroded or the pin pushed back on the sensor.

The AMM can be grossly checked (and this sounds like a gross condition ) by measuring the output voltage (white/red wire) key on engine stalled. In the -007 you should see around a volt and a half and it should fluctuate when you exercise the accordion hose like a concertina. Or the concertina hose like an accordion. But truly and finally, swapping the amm with a known good one (junkyard is best) is the only practical eval.

If the O2 ever blips lean, you don't need to be concerned about injector wiring short to ground, so I think one of the above if truly not the FPR will fix you up. I'd bet on the AMM. Oh, by the way, before getting the meter out, be sure to check the hot wire isn't broken.
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Old 09-22-2015, 01:37 PM   #7
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As I said, I haven't had much time to really delve into anything, so I'm kinda assuming the ECU is ignoring the O2 sensor since it's more or less pegged rich but still switches lean on downrev. And as for the ECT, I thought you were asking which of the two sensors I replaced, my bad. I think it was Intermotor, I ordered it through my work's parts supplier.
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Old 09-22-2015, 01:43 PM   #8
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I'm betting on the AMM as well, however, it is super common to end up with the wrong ECT sensor if you aren't familiar with Volvos. You need the sensor designed for LH 2.2 systems. The ECU never ignores the O2 sensor once the system goes closed loop. If the ECT sensor isn't telling the ECU the engine is warmed up, it could be staying in open loop and would run very rich.
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Old 09-22-2015, 01:57 PM   #9
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The AMM can be grossly checked (and this sounds like a gross condition ) by measuring the output voltage (white/red wire) key on engine stalled. In the -007 you should see around a volt and a half and it should fluctuate when you exercise the accordion hose like a concertina. Or the concertina hose like an accordion. But truly and finally, swapping the amm with a known good one (junkyard is best) is the only practical eval.

If the O2 ever blips lean, you don't need to be concerned about injector wiring short to ground, so I think one of the above if truly not the FPR will fix you up. I'd bet on the AMM. Oh, by the way, before getting the meter out, be sure to check the hot wire isn't broken.
This is the kind of info I need lol. I was kind of leaning towards the AMM, but was hoping to be able to conclusively test it before dropping money on one. I believe it was a thread you were posting in that I was reading earlier today that said you can't actually test it outside an electronics lab. Perhaps you could elaborate? I figure there has to be some kind of output signal that needs to be within certain measurable parameters that the computer needs to see. Is there no way to measure that?

Also, I was skimming some forums on another site where someone had similar problems and ended up replacing the ECU. I seem to be having better luck finding those at an affordable price than an AMM. Maybe I'll pick one up as a spare anyway.
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Old 09-22-2015, 01:57 PM   #10
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Originally Posted by 2manyturbos View Post
You need the sensor designed for LH 2.2 systems.
One can stock the sensor for LH2.4 and use it to replace in LH2.2 (single element) applications because the common point for the dual sensor is the housing. To put it short and sweet, you only need to keep the black ones on the shelf instead of both black and blue?
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Old 09-22-2015, 02:05 PM   #11
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Originally Posted by 88_Blue_Brick View Post
I figure there has to be some kind of output signal that needs to be within certain measurable parameters that the computer needs to see. Is there no way to measure that?
You can measure the output and find curves posted, but to test you need to know the input. And like I said about "gross" the AMM needs to have a very precise relationship between the mass of the air input and its voltage output.

Quote:
Originally Posted by 88_Blue_Brick View Post
Also, I was skimming some forums on another site where someone had similar problems and ended up replacing the ECU. I seem to be having better luck finding those at an affordable price than an AMM. Maybe I'll pick one up as a spare anyway.
Yes, the ECUs (assuming you have a 554?) are cheap because they are bulletproof. The AMMs, on the other hand, are getting scarce.

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Old 09-22-2015, 02:11 PM   #12
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One can stock the sensor for LH2.4 and use it to replace in LH2.2 (single element) applications because the common point for the dual sensor is the housing. To put it short and sweet, you only need to keep the black ones on the shelf instead of both black and blue?
No. If you put the black sensor in place of the blue 2.2 sensor the engine will run off the charts rich. It's a common mistake when people install later engines in the earlier bodies. The correct sensor has to be used with each of the LH systems.
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Old 09-22-2015, 02:16 PM   #13
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No. If you put the black sensor in place of the blue 2.2 sensor the engine will run off the charts rich. It's a common mistake when people install later engines in the earlier bodies. The correct sensor has to be used with each of the LH systems.
There is no reason for that going from black to blue. The other way 'round would make sense, but the black sensor grounds the same thermistor element at the head which is separately grounded by a wire in the isolated thermistor of a blue sensor. The common mistake would be using the old blue sensor in the later engine.
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Old 09-22-2015, 02:24 PM   #14
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There is no reason for that going from black to blue. The other way 'round would make sense, but the black sensor grounds the same thermistor element at the head which is separately grounded by a wire in the isolated thermistor of a blue sensor. The common mistake would be using the old blue sensor in the later engine.
I can tell you this, I made the mistake several years ago leaving the black sensor in the engine I put into an 87 740 turbo and the result was flooding so severe the engine would require starting fluid to even fire once it was warmed up. Putting the correct blue sensor in it fixed the problem instantly. Since then, I have helped 3-4 people on here that made the same mistake and took months of swapping parts before asking for help on here. One question fixed their problems, the same question I asked above, "which sensor do you have in there?" Whether it "seems" like it will work or not, it doesn't. Try it, you won't like it.
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Old 09-22-2015, 02:35 PM   #15
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I can tell you this, I made the mistake several years ago leaving the black sensor in the engine I put into an 87 740 turbo and the result was flooding so severe the engine would require starting fluid to even fire once it was warmed up. Putting the correct blue sensor in it fixed the problem instantly. Since then, I have helped 3-4 people on here that made the same mistake and took months of swapping parts before asking for help on here. One question fixed their problems, the same question I asked above, "which sensor do you have in there?" Whether it "seems" like it will work or not, it doesn't. Try it, you won't like it.
To my knowledge, this could be absolutely true for a 7 series.

In a 2 series, the blue sensor is a thermistor connected to the two pins, isolated from the case. One of those two pins is grounded and the other connects to the fuel ECU.

When EZK arrived for the 2 series, the sensor changed color and the same thermistor element used in the old blue one was used twice in the black one. The common of these two is the case, or ground. If you put one into an LH2.2 (which does not pair up with EZK in a 240) the ground wire going to the second pin is irrelevant, and the same behavior results because an identical thermistor element is used in the same circuit.

Could be there are more sensors than just two for Volvos and the color certainly does not define them, so your question about part number is the correct way to be sure.
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Old 09-22-2015, 02:35 PM   #16
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So I checked the AMM. I had 1.43v at the White/Red wire that fluctuated .2v when compressing the hose. The last time I had the AMM out (about a week ago) it looked clean and the hot wire was in one piece. I'm still thinking I need an AMM though.
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Old 09-22-2015, 02:46 PM   #17
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You had it correct in your first post, there is no real test for an AMM that is going bad, other than checking the hot wire. They can pass all the published tests with flying colors and make an engine run like poop.
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Old 09-22-2015, 02:48 PM   #18
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To my knowledge, this could be absolutely true for a 7 series.

In a 2 series, the blue sensor is a thermistor connected to the two pins, isolated from the case. One of those two pins is grounded and the other connects to the fuel ECU.

When EZK arrived for the 2 series, the sensor changed color and the same thermistor element used in the old blue one was used twice in the black one. The common of these two is the case, or ground. If you put one into an LH2.2 (which does not pair up with EZK in a 240) the ground wire going to the second pin is irrelevant, and the same behavior results because an identical thermistor element is used in the same circuit.

Could be there are more sensors than just two for Volvos and the color certainly does not define them, so your question about part number is the correct way to be sure.
That's good to know. I'm just prodding you because there is more than one way to interpret what you said above.
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Old 09-22-2015, 02:53 PM   #19
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Alright, just checked the numbers on my AMM. The number printed on the sensor is 0280212016. Isn't that for the LH 2.4 system found on '89 and up 240's? Mine is an '88. Shouldn't that have a 0280212007 and LH 2.2 system, and wouldn't that make it run like poop? I checked the ECU, and it's 0 280 000 554, which, correct me if I'm wrong, is also an LH 2.2 ECU.
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Old 09-22-2015, 03:00 PM   #20
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Alright, just checked the numbers on my AMM. The number printed on the sensor is 0280212016. Isn't that for the LH 2.4 system found on '89 and up 240's? Mine is an '88. Shouldn't that have a 0280212007 and LH 2.2 system, and wouldn't that make it run like poop? I checked the ECU, and it's 0 280 000 554, which, correct me if I'm wrong, is also an LH 2.2 ECU.
Sounds like you have a suspect. It should indeed be an 007, because for one thing, the ECU expects a resistance set on the CO mixture terminal which exists in the 007 and not on the 016. Other ways, they are similar, as an 007 will run in the LH2.4 system with its adaptive means for making that compensation.
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Old 09-22-2015, 03:08 PM   #21
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Well, I guess I know what my next purchase will be. Also, do you have any idea how to remove rear window louvers without breaking them? There's so much grime on my rear windshield that I can't see a damn thing.
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Old 09-22-2015, 03:08 PM   #22
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That's good to know. I'm just prodding you because there is more than one way to interpret what you said above.
You've piqued my interest in the 740 but I have not read the reference material. Does the EZK 117 use a head temperature sensor like 116 does?

And there's one good reason for me NOT to say what I said: If I use a black sensor in a car that needs a blue one, the next guy to work on it will have an AHA moment whether deserved or not. I fail to consider what might happen if someone in my family needs to get the car fixed while on vacation, etc. Certainly a bad idea for a pro.
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Old 09-22-2015, 03:11 PM   #23
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Well, I guess I know what my next purchase will be. Also, do you have any idea how to remove rear window louvers without breaking them? There's so much grime on my rear windshield that I can't see a damn thing.
I do not know. But I've come to understand they are desirable accessories. You may find a way to pay for that AMM.
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Old 09-22-2015, 03:21 PM   #24
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I do not know. But I've come to understand they are desirable accessories. You may find a way to pay for that AMM.
I know lol. That's why I don't want to break it. I really like it though, so I don't plan on selling it unless I NEED the cash, but I still don't know how to take the damn thing off. I'm afraid of cracking it.
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Old 09-22-2015, 04:11 PM   #25
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